Evidence for cross-modal plasticity in adult mouse visual system
Since the pioneering work of Hubel and Wiesel in the ’60, research in cat, monkey and humans has led to a central dogma that beyond the critical period the brain only retains a reduced capacity for reorganization. Current work in rodents however challenges this view since specifi c treatments are capable of reinstating cortical plasticity in the adult. The goal of our work was to study this adult cortical reorganization in detail. A combination of deprivation of one eye and stimulation of the remaining eye previously led to the identifi cation of input-specifi c subdivisions (Van Brussel et al. 2009). Using this information as a reference map, we established to what extent each of these functional subdivisions take part in cortical reorganization upon enucleation. Briefl y, there seemed to be two waves of recovery, the fi rst characterized by the expansion of the supragranular binocular zone of V1 and V2L and the second affecting the infragranular layers, initiated at the outer border of the visual cortex with neighboring non-visual cortex and accompanied by hyper-activity of this adjacent cortex. To test a possible non-visual nature of this recovery, we combined monocular enucleation with the inactivation of the remaining eye or a second sensory modality. Both lack of complete visual cortex deactivation upon enucleation of the remaining eye, and strong effects of auditory and somatosensory deprivation on infragranular visual cortex suggest cross-modal plasticity in adult mice.